Steam generator (S/G) inspections and repairs are a major component of the aging commercial pressure water reactor (PWR) nuclear industry refueling outage duration. As power producers enter the deregulated market, the need to shorten outage duration, dose and cost is more important than ever. Steam generator inspections are a high-end technology, which is constantly changing, and are a major portion of each unit's outage cost. The work occurs in the primary system, which is one of the highest radiation areas in the plant. The speed at which a S/G inspection is conducted is critical to decreasing the outage duration, dose and cost. These metrics are used by the nuclear industry to measure efficiency, planning, compliance and control during outages.
Existing S/G inspection systems include a leg anchored to a tube sheet. The leg provides vertical motion for a three-axis arm to facilitate the required inspections and repairs. During S/G inspections, the manipulator arm must be repositioned relative to the S/G plenum to access the entire surface of the tube. This repositioning of the manipulator arm adds time, dose and significant preplanning to minimize the number of moves required during the inspection/repair campaign.
Generally, two platform workers located outside the S/G reposition the manipulator arm using a block and tackle and long poles. Whenever the manipulator is repositioned, the potential for robot damage is significantly increased due to the fact that the manipulator arm must be removed from the S/G plenum prior to repositioning and re-installed after repositioning is complete. Additionally, during an inspection, it is vital to maintain the arm parallel with the tube sheet for proper operation of various tooling. Frequently, platform workers are required to straighten the leg during repair activities to keep the arm straight.
Consequently, there is a need for a S/G inspection system that permits repositioning of a S/G manipulator arm without having to remove the arm from the anchored leg. Additionally, there is a need for a S/G inspection system that facilitates repositioning both the anchored leg and manipulator arm relative to the S/G.